In the case of LSI manufacturing, first, samples of several transistors (MOSFET) with a different shape (size) of a channel length L, channel width W, and so on of a gate of the transistor (MOSFET or an element similar to the MOSFET) are tested in the manufacturing line. Next, from the measurement result of an electric property of a tested piece, a great number of model parameters of the circuit (and element) design model of the transistor are adjusted (fitted) so as to conform with the transistor property which is manufactured in the manufacturing line with a high degree of accuracy. Simulation of various types of LSI (transistor) which are manufactured in the manufacturing line by the heretofore known circuit simulator such as SPICE was carried out by using the circuit design model of the transistor.
Taking the MOSFET which is used the most in the world as an example, several models are proposed as the circuit design model of the transistor. Conventionally, the heretofore known BSIM (Berkeley Short Channel IGFET Model) is mainly used for the above-mentioned simulation. The BSIM expresses a relationship among a Vg (gate voltage), Vd (drain voltage), Vb (bulk voltage), and Id (drain current) and so on by a great number of formulas including a variable such as the channel length L, channel width W, and so on of the gate, and a great number of parameters. However, the BSIM consists of a large number of formulas, and the number of basic parameters alone which should be adjusted has more than 50 parameters, so that adjustment of the parameters was difficult. Also, if a field without actual measurement value is extrapolated and simulated, the chance of an error increases.
Consequently, a new type of circuit design model named HiSIM (Hiroshima-university STARC IGFET Model) which is a surface potential model wherein a formula for analysis is derived based on surface potential, has been recently developed and disclosed by Miura, one of the inventors of the present invention. The HiSIM wherein the transistor property is described by using the surface potential has a small number of parameters compared to the conventional BSIM which is indicated as a function of an external voltage, and even if the HiSIM is extrapolated, a high-accuracy simulation can be performed. Incidentally, since details of the HiSIM and conventional parameter adjusting means in the HiSIM are described in the following publication available for downloading from the following URL, detailed explanations are omitted.
Japanese Nonpatent Publication 1: HiSIM 1.1.1 User's Manual
Also, conventionally, a parameter adjusting device that automatically performs the parameter fitting (adjusting) processing of a physical model including a great number of parameters using a genetic algorithm from an experimental result and so on, is proposed. For example, in the following publication previously submitted for a patent by the inventors of the present invention, a commonly-used parameter adjusting device that automatically performs the parameter adjusting processing of a physical model including a great number of parameters using the genetic algorithm, is proposed.
Japanese Patent Publication 1: Japanese Patent Publication No. 2003-108972